手写bind实现

Function.prototype.bind = function(thisArg) {
  if (typeof this !== 'function') return;
  const _self = this;
  const args = Array.prototype.slice.call(arguments, 1)
  const f = function() {
    return Reflect.apply(_self, this instanceof _self ? this : (thisArg || window), args.concat(Array.prototype.slice.call(arguments))); // 注意参数的处理
  }
  f.prototype = this.prototype
  return f
}

Function.prototype.bind1 = function(thisArg, ...args) {
  if (typeof this !== 'function') return;
  const _self = this;
  const f = function() {
    return Reflect.apply(_self, this instanceof _self ? this : (thisArg || window), args.concat(Array.from(arguments))); // 注意参数的处理
  }
  f.prototype = this.prototype
  return f
}

function foo(name) {
  this.name = name;
}
const obj = {}

const bar = foo.bind1(obj)
bar('mary') // obj { name: 'mary' }
const tom = new foo('tom') // foo { name: 'tom' }

Function.prototype.call = function(thisArg, ...args) {
  thisArg.tempFn = this
  const result = thisArg.tempFn(...args)
  Reflect.deleteProperty('tempFn')
  return result
}

Function.prototype.apply = function(thisArg, ...args) {
  thisArg.tempFn = this
  const result = thisArg.tempFn(args)
  Reflect.deleteProperty('tempFn')
  return result
}